Fibre loss and distribution in skeletal muscle from patients with severe peripheral arterial insufficiency.

Cross-sections of whole calf muscles (m soleus and m gastrocnemius) were obtained from five previously clinically health individuals who had died accidentally (controls) and from amputated legs of five patients of similar age with severe peripheral arterial insufficiency. In the controls, but not in the patients, a characteristic distribution of different fibre types over the entire cross-sections was found, with a relative increase in number of (slow twitch) type 1 fibres in the central parts of both m soleus and m gastrocnemius. A pronounced neuromuscular pathomorphology was found in the patients, especially in m gastrocnemius. The findings suggested widespread damage to the fibres. There was also a lower total number of fibres in these ischaemic muscles; about 50% of the fibres of m gastrocnemius seemed to have disappeared. The results suggested that the relative inactivity as such may be responsible for some of the structural changes, above all the dedifferentiated distribution of different fibres over the cross-section. However, repeated acute and chronic subacute ischaemia may also cause, in the long term, irreparable damage and loss of many individual fibres. This may explain why muscles of patients with peripheral arterial insufficiency are also weaker, during single contractions. The lack of corresponding muscular atrophy in these patients seems to a large extent to be explained by an increase in connective tissue.